1. Field of the Invention
The present invention relates to a film positioning system and a method thereof, and more particularly, is suitably applied to a telecine device which converts images recorded on a cinefilm into a video signal, for example.
2. Description of the Related Art
In a telecine device, one frame of images recorded on a cinefilm is positioned on the optical axis of a video camera, and a source light is entered into the pickup system of the video camera through the cinefilm in this state. Thereby, the above positioned frame image is picked up by the video camera.
Moreover, after completing the pickup of the one frame image in this manner, the telecine device feeds the cinefilm and positions the next frame on the optical axis, and performs a similar pickup in this state, so that the images sequentially recorded on the cinefilm are converted into video signals (hereinafter, it is referred to as telecine processing).
In such a telecine device, an intermittent film feeder is provided to intermittently feed a cinefilm frame by frame. In the intermittent film feeders, there are two kinds of intermittent feeding systems, by mechanical control in that the gear teeth of sprockets are engaged with perforations provided on the both ends of the cinefilm in its width direction (sprocket holes on the film) and the above sprockets are intermittently rotated through, e.g., Geneva gears, so that a cinefilm is intermittently fed, and by electronic control in that a motor itself for rotating sprockets is intermittently and rotationally driven, so that a cinefilm is intermittently fed.
In the intermittent feeding system by mechanical control, when the machine is finely regulated, positioning accuracy of a cinefilm becomes fine by being used with a registration pin, so that image pause performance is improved.
By the way, with respect to a feed length per frame in cinefilms, for instance, a feed length corresponding to four perforations is a standard format in a 35 mm film. Other than that, there is a format for high quality mode in which a feed length per frame corresponds to eight perforations, a format for reducing the running cost of a film in which a feed length corresponds to three perforations per frame, etc. Furthermore, recently, various film formats such as a film format of two half perforations per frame, and a film format considering a combinability with a 16 mm film, exist. Therefore, an intermittent film feeder which can easily adapt to these formats and is economical is desired.
However, in the above intermittent film feeder in the intermittent feed system by mechanical control, since its intermittent feed operation is mechanical, it is difficult to adapt to various film formats. Moreover, in some cinefilms, perforation pitch changes as the film itself changes over the years. Since the intermittent film feeder by mechanical control basically adapts to only perforations at a prescribed pitch, if a cinefilm with changed perforation pitch is intermittently fed, there is a possibility of damaging the film itself.
On the other hand, in an intermittent film feeder 200 by the intermittent feeding system by electronical control, as shown in FIG. 1, one intermittent feed sprocket 202 is provided to intermittently feed a cinefilm 201 which is supplied from a supply reel (not shown in FIG. 1) on a supply side to a winding reel (not shown) on a winding side.
Furthermore, the intermittent film feeder 200 guides the above cinefilm 201 while regulating a feed position of the cinefilm 201 by a film gate 203 at a position on the axis of a video camera (not shown).
The intermittent film feeder 200 has one continuous feed sprocket (not shown) on the supply side and the winding side of the cinefilm 201 respectively. In the state where a flection 210 is generated between the continuous feed sprocket on the supply side and the film gate 203, and between the continuous feed sprocket on the winding side and the intermittent feed sprocket 202, respectively, the cinefilm 201 is intermittently fed by being pressed to the film gate 203 under a prescribed pressure with a skate press 204 while rotationally driving the intermittent feed sprocket 202.
This intermittent feed sprocket 202 is rotationally driven by a DC servomotor (not shown), and the above cinefilm 201 is intermittently fed in the state where the gear teeth are engaged with perforations provided at the both ends of the cinefilm 201 in the width direction. A certain gap is provided in the forward direction of the above perforations so that the gear teeth of the intermittent feed sprocket 202 are smoothly engaged with and disengaged from the perforations of the cinefilm 201 at this time.
Furthermore, the intermittent feed sprocket 202 starts and stops so as to position the cinefilm 201 for each frame by electronical control such as a drive motor or a cam. That is, the intermittent feed sprocket 202 is rotationally driven so as to position the gear teeth pulling the cinefilm 201 to a fixed angle, and the rigidity of the gear teeth is set sufficiently large comparing the film load of the cinefilm 201.
The skate press 204 is a pressing mechanism to generate a friction F.sub.p for positioning the frames of the cinefilm 201 stably. For instance, a pressure of 15N degrees is applied to the 35 mm cinefilm 201, so that a friction F.sub.p of 4.5N degrees is generated in a direction reverse to the forward feeding direction CW. If the friction F.sub.p by this skate press 204 is not generated, the feed operation itself for the cinefilm 201 by the intermittent feed sprocket 202 can be performed, however, when the intermittent feed sprocket 202 is stopped, a stable positioning operation cannot be executed because overrun occurs in which a film does not stop at a stop position, owing to the inertia force of the cinefilm 201.
Moreover, in recent years, the intermittent feeding operation for the cinefilm 201 can be performed at a high speed of 48 frame/sec or more. In such a case, a larger friction F.sub.p by the skate press 204 is required on the execution of stable positioning of the cinefilm 201.
In such a telecine device, when the cinefilm 201 is intermittently fed frame by frame by the intermittent film feeder 200, the friction F.sub.p by the skate press 204 is applied to the both ends (edge parts) of the cinefilm 201. Recently, however, since control data such as a digital audio signal and a time code is recorded in these parts, there has been a problem that the friction F.sub.p by the skate press 204 damages the digital audio signal and the control data or the like.
Furthermore, in a telecine device, when the cinefilm 201 is intermittently fed frame by frame by the intermittent film feeder 200, if the friction F.sub.p to be applied was not adjusted according to the differences of the above cinefilm 201 in its kind or being new or old or the like, it is difficult to execute a stable positioning. Even if that can be adjusted, there has been a problem that stable positioning operation cannot be performed since a friction F.sub.p to be applied to the film changes as the film condition changes with the cinefilm 201 run.